To minimize ground movement while tunneling a sewer 5 m below Toronto's Spadina subway line, engineers used special instrumentation, tunneling control and grouting to limit settlements without interrupting subway service. In one of only a few North American applications, engineers used compensation grouting to control ground movement during tunneling of a 1.1 km sewer line through difficult soil conditions. In order to maintain gravity flow, the sewer had to be tunneled beneath the Toronto's Spadina subway line during construction of a new station on the Eglinton subway line. Engineers working on the project developed an elaborate settlement monitoring system to ensure safe subway operation through the project. The cost of the entire sewer relocation project, in Canadian dollars, was $6 million.